Liquid jet head and liquid jet apparatus

ABSTRACT

Provided are a liquid jet head capable of preventing occurrence of crosstalk and obtaining a stable liquid ejecting property and a liquid jet apparatus. Partitions  11  at both sides in a width direction of a pressure generating chamber  12  are provided so as to extend to the vicinity of an end of a reservoir portion  32  at the pressure generating chamber  12  side. Liquid supply paths  14  and communicating paths  100  are provided by being divided for each of the pressure generating chambers  12  by the partitions  11  (wall portions  11   a ). Specifically, each of the liquid supply paths  14  communicates with the pressure generating chamber  12  and is formed to have a width smaller than that of the pressure generating chamber  12 , and each of the communicating paths  100  allows the liquid supply path  14  and a communicating portion  13  to communicate with each other and is formed to have a width larger than that of the liquid supply path  14 . Thus, occurrence of crosstalk can be prevented and a stable liquid ejecting property can be obtained.

TECHNICAL FIELD

The present invention relates to a liquid jet head which ejects liquiddroplets and a liquid jet apparatus. Particularly, the present inventionrelates to an ink-jet recording head which ejects ink droplets fromnozzle orifices and an ink-jet recording apparatus.

BACKGROUND ART

A following ink-jet recording head has been put to practical use.Specifically, in the ink-jet recording head, a part of pressuregenerating chambers communicating with nozzle orifices for ejecting inkdroplets is formed of a vibration plate, this vibration plate isdeformed by piezoelectric elements, ink in the pressure generatingchambers is pressurized and thus the ink droplets are ejected from thenozzle orifices. For example, as the ink-jet recording head describedabove, there is one in which a uniform piezoelectric material layer isformed over an entire surface of the vibration plate by use of adeposition technology, this piezoelectric material layer is cut into ashape corresponding to pressure generating chambers by use of alithography method and piezoelectric elements are formed so as to beindependent for each of the pressure generating chambers. There is aproblem that such piezoelectric elements are prone to be damaged due toexternal environments such as moisture (humidity). For example, in areservoir that is a common liquid chamber of the pressure generatingchambers, ink containing moisture is filled. Thus, it is required tosecure a certain distance between the reservoir and the piezoelectricelements.

Here, as a structure for preventing such damage to the piezoelectricelements, Japanese Patent Laid-Open No. 2000-296616, for example,discloses a structure in which a reservoir forming plate having apiezoelectric element holding portion is joined with a passage-formingsubstrate having pressure generating chambers formed therein, andpiezoelectric elements are sealed in this piezoelectric element holdingportion. Specifically, the structure includes: a passage-formingsubstrate in which a plurality of pressure generating chamberscommunicating with nozzle orifices are provided; piezoelectric elementswhich cause pressure changes in the respective pressure generatingchambers; a reservoir forming plate in which a reservoir portionconstituting at least a part of a reservoir, that is a common liquidchamber of the pressure generating chambers, is provided; and a nozzleplate which is joined with an opposite surface side of thepassage-forming substrate and has nozzle orifices. In addition, in aregion of the reservoir forming plate which faces the piezoelectricelements, a piezoelectric element holding portion is provided, which, ina state of securing a space without inhibiting movement of thepiezoelectric elements, can seal the space. Note that, at one end of therespective pressure generating chambers in a longitudinal direction, inksupply paths for supplying ink in the reservoir to the respectivepressure generating chambers are provided.

However, even in the above-described head structure in which thepiezoelectric elements are formed in the piezoelectric element holdingportion, the piezoelectric elements are likely to be damaged by moisturecontained in the ink in the reservoir if the moisture permeates ajunction portion between the passage-forming substrate and the reservoirforming plate and enters into the piezoelectric element holding portion.Therefore, in either case, it is required to secure a sufficientdistance between the piezoelectric elements and the reservoir portion,more specifically, a sufficient length of a junction portion between thepiezoelectric element holding portion and the reservoir. Meanwhile, inorder to improve an ink supply property, it is required to shorten alength of the ink supply path. Thus if sufficiently securing thejunction portion between the piezoelectric element holding portion andthe reservoir is attempted, a space formed of only the passage-formingsubstrate is formed along an arrangement direction of the pressuregenerating chambers between the ink supply paths and the reservoir.

In the ink-jet recording head having the structure as described above,in: ejection of the ink, because of pressure changes caused in thepressure generating chambers, the ink in the pressure generatingchambers flows out toward the reservoir through the ink supply pathssimultaneously with the ink ejection. Thus, if there exists the spaceformed of only the passage-forming substrate between the respective inksupply paths and the reservoir, the ink flowing out toward the reservoirfrom the respective pressure generating chambers flows in bothdirections within the space, including the arrangement direction of thepressure generating chambers (a nozzle arrangement direction) and thelongitudinal direction of the pressure generating chambers (a directionorthogonal to the nozzle arrangement direction). Thus, there is aproblem that flows of the ink flowing out from adjacent pressuregenerating chambers interfere with each other to cause a so-calledcrosstalk and a stable ink ejecting property cannot be obtained.

Note that, if the junction portion between the piezoelectric elementholding portion and the reservoir is shortened in accordance with thelength of the ink supply path, a junction area between thepassage-forming substrate and the reservoir forming plate is reduced.Thus, sufficient junction strength cannot be obtained. Moreover, if theink supply path is formed to be relatively long in order to secure thejunction portion between the piezoelectric element holding portion andthe reservoir, a cross-section area of the ink supply path issubstantially increased. Thus, there arises a problem that a dampingproperty of meniscus is lowered and high-speed drive becomes impossibleto perform.

Note that, needless to say, such problems as described above similarlyexist not only in the ink-jet recording head for ejecting ink but alsoin another liquid jet head for ejecting a liquid other than ink.

DISCLOSURE OF THE INVENTION

In consideration for the circumstances as described above, the object ofthe present invention is to provide a liquid jet head capable ofpreventing occurrence of crosstalk and obtaining a stable liquidejecting property and a liquid jet apparatus.

A first aspect of the present invention for solving the foregoing objectis a liquid jet head which includes: a passage-forming substrate inwhich a plurality of pressure generating chambers communicating withnozzle orifices are arranged; piezoelectric elements which are providedon the passage-forming substrate with a vibration plate interposedtherebetween and each of which includes a lower electrode, apiezoelectric layer and an upper electrode; and a reservoir formingplate which is joined with a surface of the passage-forming substrate atthe piezoelectric element side and has a reservoir portion providedtherein, the reservoir portion constituting a part of a reservoir thatis a common liquid chamber of the respective pressure generatingchambers. In the liquid jet head, the reservoir is formed of thereservoir portion and a communicating portion provided in thepassage-forming substrate. In addition, partitions at both sides in awidth direction of the pressure generating chambers are provided so asto extend to the vicinity of an end of the reservoir portion at thepressure generating chamber side. Thus, liquid supply paths andcommunicating paths are provided while being separated for each of thepressure generating chambers by the partitions. Specifically, each ofthe liquid supply paths communicates with each of the pressuregenerating chambers and has a width smaller than that of the pressuregenerating chamber. Moreover, each of the communicating paths allows theliquid supply path and the communicating portion to communicate witheach other and has a width larger than that of the liquid supply path.

In the first aspect, since the communicating paths are provided betweenthe respective liquid supply paths and the reservoir, respectively,occurrence of crosstalk is prevented and a stable liquid ejectingproperty is obtained.

A second aspect of the present invention is the liquid jet headaccording to the first aspect, characterized in that a relationshipbetween the width w₁ of the communicating path and the width w₂ of thepressure generating chamber satisfies w₁≧w₂.

In the second aspect, a desired liquid supply property can be ensured.

A third aspect of the present invention is the liquid jet head accordingto one of the first and second aspects, characterized in that arelationship between the width w₁ of the communicating path and thewidth w₃ of the liquid supply path satisfies w₁≧2×w₃.

In the third aspect, since the communicating path is formed to have apredetermined size, a desired liquid supply property can be ensured.

A fourth aspect of the present invention is the liquid jet headaccording to any one of the first to third aspects, characterized inthat a length of the communicating path is equal to or longer than athickness of the passage-forming substrate.

In the fourth aspect, by providing the communicating path having alength which is equal to or longer than a predetermined length,occurrence of crosstalk is more effectively prevented.

A fifth aspect of the present invention is the liquid jet head accordingto any one of the first to fourth aspects, characterized in that adistance between an end of each of the partitions at the reservoirportion side and the reservoir portion is shorter than the thickness ofthe passage-forming substrate.

In the fifth aspect, since the end of the partition at the reservoirportion side is provided so as to extend to the vicinity of an end ofthe reservoir portion at the pressure generating chamber side,occurrence of crosstalks is prevented.

A sixth aspect of the present invention is the liquid jet head accordingto any one of the first to fifth aspects, characterized in that thepiezoelectric elements are covered with an insulating film made of aninorganic insulating material.

In the sixth aspect, since the piezoelectric layer is covered with aninsulating film made of an inorganic insulating material having a lowmoisture permeation rate, deterioration (destruction) of thepiezoelectric layer (piezoelectric elements) due to moisture (humidity)is surely prevented over a long period of time.

A seventh aspect of the present invention is the liquid jet headaccording to the sixth aspect, characterized in that the insulating filmis made of Al₂O₃.

In the seventh aspect, since the piezoelectric elements are covered withan insulating film made of a metallic oxide having an extremely lowmoisture permeation rate, destruction of the piezoelectric layer due toexternal environments is surely prevented.

An eighth aspect of the present invention is the liquid jet headaccording to any one of the first to seventh aspects, characterized inthat, in the reservoir forming plate, a piezoelectric element holdingportion capable of securing a space without inhibiting movement of thepiezoelectric elements is provided in a region which faces thepiezoelectric elements. Moreover, a region between the piezoelectricelement holding portion and the reservoir portion in the reservoirforming plate is a junction portion between the reservoir forming plateand the passage-forming substrate.

In the eighth aspect, by providing the partitions so as to be extendedto the vicinity of a boundary of the junction portion, between thepassage-forming substrate and the reservoir forming plate, at thereservoir portion side, rigidity of the both members is ensured.Moreover, by providing the communicating paths, respectively, betweenthe liquid supply paths and the communicating portion, occurrence ofcrosstalk is prevented.

A ninth aspect of the present invention is the liquid jet head accordingto the eighth aspect, characterized in that ends of the partitions atthe reservoir portion side are positioned in a region which faces thejunction portion.

In the ninth aspect, since the ends of the partitions protrude in thecommunicating portion, it is possible to surely prevent the partitionsfrom obstructing formation of the reservoir.

A tenth aspect of the present invention is the liquid jet head accordingto one of the eighth and ninth aspects, characterized in that a lengthof the junction portion is equal to or longer than 200 μm.

In the tenth aspect, since the junction portion between thepassage-forming substrate and the reservoir forming plate, the junctionportion being positioned at the one end of the pressure generatingchambers in the longitudinal direction, is formed to have a length whichis equal to or longer than a predetermined length. Therefore, moisturecontained in a liquid in the reservoir never actually permeates into thepiezoelectric element holding portion. Thus, destruction of thepiezoelectric elements is prevented. Moreover, the rigidity of thepassage-forming substrate and the reservoir forming plate is enhanced.

An eleventh aspect of the present invention is the liquid jet headaccording to any one of the eighth to tenth aspects, further includingan air release hole which has one end communicating with thepiezoelectric element holding portion and the other end released to theatmosphere.

In the eleventh aspect, since the piezoelectric element holding portionis released to the atmosphere through the air release hole, no dewcondensation occurs in the piezoelectric element holding portion. Thus,destruction of the piezoelectric elements due to the dew condensation issurely prevented.

A twelfth aspect of the present invention is the liquid jet headaccording to any one of the first to eleventh aspects, characterized inthat the thickness of the passage-forming substrate is equal to orshorter than 100 μm.

In the twelfth aspect, the pressure generating chambers can be arrangedrelatively densely while maintaining rigidity of the partitions betweenthe adjacent pressure generating chambers.

A thirteenth aspect of the present invention is the liquid jet headaccording to any one of the first to twelfth aspects, characterized inthat the pressure generating chambers are formed by subjecting a singlecrystal silicon substrate to an anisotropic etching process.

In the thirteenth aspect, a liquid jet head having high-density nozzleorifices can be relatively easily manufactured.

A fourteenth aspect of the present invention is a liquid jet apparatusincluding the liquid jet head according to any one of the first tothirteenth aspects.

In the fourteenth aspect, it is possible to realize a liquid jetapparatus with a substantially stabilized liquid ejecting property andimproved reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a head according to embodiment1.

FIGS. 2( a) and 2(b) area plan view and a cross-sectional view of thehead according to embodiment 1.

FIG. 3 is a cross-sectional view showing a passage structure of the headaccording to embodiment 1.

FIG. 4 is a cross-sectional view of another head according to embodiment1.

FIG. 5 is a graph showing a relationship between the number ofsimultaneous ejections and a crosstalk rate.

FIGS. 6( a) to 6(d) are cross-sectional views showing steps ofmanufacturing the head according to embodiment 1.

FIGS. 7( a) to 7(d) are cross-sectional views showing the steps ofmanufacturing the head according to embodiment 1.

FIG. 8 is a schematic view showing an example of a recording head.

BEST MODE FOR IMPLEMENTING THE PRESENT INVENTION

The present invention will be described in detail below based onembodiments.

Embodiment 1

FIG. 1 is an exploded perspective view of an ink-jet recording headaccording to embodiment 1. FIG. 2( a) is a schematic plan view of FIG. 1and FIG. 2( b) is a cross-sectional view along the line A-A′ in FIG. 2(a). As shown in FIGS. 1 and 2, a passage-forming substrate 10 is made ofa single crystal silicon substrate of plane orientation (110) in thisembodiment. On both surfaces of the substrate, an elastic film 50, whichis made of silicon dioxide previously formed by thermal oxidation, and amask pattern 51, which is used as a mask in forming pressure generatingchambers to be described later, are provided, respectively.

In the passage-forming substrate 10 described above, pressure generatingchambers 12 are arranged in a width direction of the substrate, that is,arranged in parallel with a nozzle arrangement direction. Specifically,the pressure generating chambers 12 are formed by subjecting thesubstrate to an anisotropic etching process from its opposite surfaceside and are separated from each other by a plurality of partitions 11.Moreover, at one end of the pressure generating chambers 12 in alongitudinal direction (in a direction orthogonal to the nozzlearrangement direction), in addition to the pressure generating chambers12, ink supply paths 14, communicating paths 100 and a communicatingportion 13, which forms a part of a reservoir 110 to be a common inkchamber of the respective pressure generating chambers 12, are formed.

Each of the ink supply paths 14 communicates with the one end of thepressure generating chamber 12 in the longitudinal direction and has asmaller cross-section area than that of the pressure generating chamber12. For example, in this embodiment, the ink supply path 14 is formed tohave a smaller width than that of the pressure generating chamber 12 insuch a manner that a passage at the pressure generating chamber 12 sidebetween the reservoir 110 and the pressure generating chamber 12 isnarrowed in a width direction of the pressure generating chamber. Notethat, as described above, in this embodiment, the ink supply path 14 isformed by narrowing the width of the passage from one side. However, theink supply path may be formed by narrowing the width of the passage fromboth sides. Moreover, each of the communicating paths 100 is formed insuch a manner that the partitions 11 at both sides in the widthdirection of the pressure generating chamber 12 are provided so as toextend toward the communicating portion 13 and a space between the inksupply path 14 and the communicating portion 13 is separated. Note thatthe communicating path 100 will be described later in detail.

Here, anisotropic etching is performed by utilizing a difference in anetching rate of the single crystal silicon substrate. For example, inthis embodiment, when the single crystal silicon substrate is dipped inan alkaline solution such as KOH, the substrate is gradually eroded andthere appear a first (111) plane perpendicular to the (110) plane and asecond (111) plane. The angle formed by the meeting of the second (111)plane and the first (111) plane is approximately 70 degrees, and theangle formed by the meeting of the second (111) plane and the foregoing(110) plane is approximately 35 degrees. Accordingly, an etching rate ofthe (111) planes is compared to that of the (110) plane. Thus, theanisotropic etching is performed by utilizing a characteristic that theetching rate of the (111) planes is about 1/180 of that of the (110)plane. By use of the anisotropic etching, high-precision processing canbe performed by taking depth processing to form a parallelogram shape,which is formed by two of the first (111) planes and two of the obliquesecond (111) planes, as its basis. Therefore, the pressure generatingchambers 12 can be arranged in the high density.

In this embodiment, long sides of each pressure generating chamber 12are formed of the first (111) planes and short sides thereof are formedof the second (111) planes. This pressure generating chamber 12 isformed by performing etching up to the elastic film 50 while nearlypenetrating the passage-forming substrate 10. Here, an extremely smallpart of the elastic film 50 is dipped in the alkaline solution used inetching the single crystal silicon substrate.

A thickness of the passage-forming substrate 10 as described above maybe selected to be optimum in accordance with a density of arrangement ofthe pressure generating chambers 12. For example, in the case ofdisposing about 180 of the pressure generating chambers 12 per inch (180dpi), the thickness of the passage-forming substrate 10 may be set toabout 220 μm Moreover, in the case of disposing the pressure generatingchambers 12 as relatively densely as, for example, 200 dpi or more, itis preferable that the passage-forming substrate 10 is formed to be asrelatively thin as 100 μm or less, particularly 70 μm. This is becausethe density of arrangement of the pressure generating chambers 12 can beincreased while maintaining rigidity of the partitions 11 between theadjacent pressure generating chambers 12.

Moreover, at the open face side of the passage-forming substrate 10, anozzle plate 20 having nozzle orifices 21 drilled therein is joined. Thenozzle plate 20 as described above is made of glass ceramics, a singlecrystal silicon substrate, stainless steel or the like with a thicknessof, for example, 0.05 to 1 mm. The nozzle plate 20 entirely covers theone surface of the passage-forming substrate 10 with its one surface andalso serves as a reinforcing plate which protects the passage-formingsubstrate 10 from impact and external force. Here, a size of thepressure generating chamber 12 for applying an ink droplet ejectingpressure to ink and a size of the nozzle orifice 21 for ejecting inkdroplets are optimized in accordance with an amount of ink droplets tobe ejected, an ejecting speed and an ejecting frequency. For example, inthe case of recording 360 of ink droplets per inch, it is required toform the nozzle orifice 21 with a diameter of several ten μm with highprecision.

Meanwhile, on the elastic film 50 having a thickness of, for example,about 1.0 μm at the opposite side to the open face of thepassage-forming substrate 10, a lower electrode film 60 having athickness of, for example, about 0.2 μm, a piezoelectric layer 70 havinga thickness of, for example, about 1.0 μm and an upper electrode film 80having a thickness of, for example, about 0.05 μm are laminated in aprocess to be described later. Those electrode films and piezoelectriclayer are laminated on the elastic film 50 with an insulating film 55with a thickness of, for example, 0.4 μm interposed therebetween andconstitute a piezoelectric element 300. Here, the piezoelectric elements300 mean a part including the lower electrode film 60, the piezoelectriclayer 70 and the upper electrode film 80. In general, the piezoelectricelements 300 are formed by using any one of the electrodes thereof as acommon electrode and patterning the other electrode and thepiezoelectric layer 70 for each of the pressure generating chambers 12.Consequently, here, a part which includes any one of the electrodespatterned and the piezoelectric layer 70, and in which piezoelectricstrain occurs due to voltage application to the both electrodes, iscalled a piezoelectric active portion. In this embodiment, the lowerelectrode film 60 is used as the common electrode of the piezoelectricelements 300 and the upper electrode film 80 is used as an individualelectrode thereof. However, even if this order is reversed because of adrive circuit and wiring, there is no trouble caused thereby. In eithercase, the piezoelectric active portion is formed in each pressuregenerating chamber. Moreover, here, the piezoelectric elements 300 andthe vibration plate displaced by drive of the piezoelectric elements 300are collectively called a piezoelectric actuator. Note that, in theexample described above, the elastic film 50, the insulating film 55 andthe lower electrode film 60 function as the vibration plate.

As a material of the piezoelectric layer 70, for example, a relaxerferroelectric substance or the like may be used, which is obtained byadding metal such as niobium, nickel, magnesium, bismuth and ytterbiumto a ferroelectric piezoelectric material such aslead-zirconate-titanate (PZT). A composition thereof may beappropriately selected in consideration of characteristics of thepiezoelectric element, use thereof and the like. For example, thefollowing compositions are enumerated, including PbTiO₃(PT), PbZrO₃(PZ),Pb(Zr_(x)Ti_(1-x))O₃(PZT), Pb(Mg_(1/3)Nb_(2/3))O₃—PbTiO₃(PMN—PT)Pb(Zn_(1/3)Nb_(2/3))O₃—PbTiO₃(PZN—PT),Pb(Ni_(1/3)Nb_(2/3))O₃—PbTiO₃(PNN—PT)Pb(In_(1/2)Nb_(1/2))O₃—PbTiO₃(PIN—PT),Pb(Sc_(1/3)Ta_(1/2))O₃—PbTiO₃(PST—PT)Pb(Sc_(1/3)Nb_(1/2))O₃—PbTiO₃(PSN—PT), BiScO₃—PbTiO₃(BS—PT),BiYbO₃—PbTiO₃(BY—PT) and the like.

Accordingly, with one end of each upper electrode film 80 that is theindividual electrode of the piezoelectric elements 300 including thepiezoelectric layer 70 as described above, a lead electrode 90 isconnected. Specifically, the lead electrode 90 is made of, for example,gold (Au) or the like and has one end extended to a region correspondingto a through-hole 33 to be described later. Moreover, the piezoelectricelements 300 are covered with an insulating film 200 made of aninorganic insulating material. For example, in this embodiment, apattern region including the respective layers constituting thepiezoelectric elements 300 and the lead electrode 90 is covered with theinsulating film 200 except a region facing connection portions 60 a and90 a of the lower electrode film 60 and the lead electrode 90, which areconnected through unillustrated drive IC and connection wirings.Specifically, surfaces (upper faces and end faces) of the lowerelectrode film 60, the piezoelectric layer 70, the upper electrode film80 and the lead electrode 90 in the pattern region are covered with theinsulating film 200.

Here, a material of the insulating film 200 as described above is notparticularly limited as long as the material is an inorganic insulatingmaterial. Although aluminum oxide (Al₂O₃), tantalum pentoxide (Ta₂O₅),silicon dioxide (SiO₂) and the like, for example, are enumerated, it ispreferable to use aluminum oxide (Al₂O₃) Particularly, in the case ofusing aluminum oxide, even if the insulating film 200 is formed to be asthin as about 100 nm, moisture permeation under a high-humidityenvironment can be sufficiently prevented. Note that, when an organicinsulating material such as resin is used, for example, as the materialof the insulating film, the moisture permeation cannot be sufficientlyprevented with the same thickness as that of the insulating film made ofthe inorganic insulating material described above. Moreover, if the filmthickness of the insulating film is increased in order to prevent themoisture permeation, there may arise a problem that movement of thepiezoelectric elements is hindered.

The insulating film 200 made of the inorganic insulating material asdescribed above has extremely low moisture permeability even if the filmis thin. Thus, by covering the surfaces of the lower electrode film 60,the piezoelectric layer 70, the upper electrode film 80 and the leadelectrode 90 with the insulating film 200 described above, destructionof the piezoelectric layer 70 due to moisture (humidity) can beprevented. Moreover, by covering the surfaces of the lead electrode 90and the respective layers constituting the piezoelectric elements 300,except the connection portions 60 a and 90 a, even if moisture entersfrom a space between these layers and the insulating film 200, it ispossible to prevent the moisture from reaching the piezoelectric layer70. Accordingly, the destruction of the piezoelectric layer 70 due tomoisture can be more surely prevented.

Moreover, on the passage-forming substrate 10 having the piezoelectricelement 300 formed thereon, a reservoir forming plate 30 is joined. Inthis reservoir forming plate 30, a reservoir portion 32 constituting apart of the reservoir 110 is provided outside the respective pressuregenerating chambers 12 in the longitudinal direction. In thisembodiment, the reservoir portion 32 is formed across the widthdirection of the pressure generating chambers 12 while penetrating thereservoir forming plate 30 in its thickness direction. In addition, thereservoir portion 32 is communicated with the communicating portion 13of the passage-forming substrate 10 through a penetrating portionprovided in the elastic film 50 and the insulating film 55 and forms thereservoir 110 to be a common ink chamber of the respective pressuregenerating chambers 12. Note that a thickness of the reservoir formingplate 30 as described above is, for example, 200 to 400 μm.

Moreover, in this embodiment, in the reservoir forming plate 30 asdescribed above, a piezoelectric element holding portion 31 capable ofsecuring a space without inhibiting movement of the piezoelectricelements 300 is provided in a region facing the piezoelectric elements300. Specifically, the piezoelectric elements 300 are formed inside thepiezoelectric element holding portion 31.

Furthermore, in this embodiment, an air release hole 31 a which has oneend communicating with the piezoelectric element holding portion 31 andthe other end being released to the atmosphere is provided in thereservoir forming plate 30 described above. Specifically, thepiezoelectric element holding portion 31 is released to the atmospherethrough the air release hole 31 a without sealing the piezoelectricelements 300 therein. Thus, occurrence of dew condensation in thepiezoelectric element holding portion 31 can be prevented. Consequently,destruction of the piezoelectric elements 300 due to the dewcondensation can be surely prevented. Note that the other end of the airrelease hole 31 a as described above is released to the atmosphere in aregion which does not interfere with, for example, wiring provided onthe opposite surface to that of the piezoelectric element holdingportion 31 of the reservoir forming plate 30, drive ICs mounted on thewiring and the like.

Moreover, the reservoir 110 of the reservoir forming plate 30 asdescribed above and the respective pressure generating chambers 12 ofthe passage-forming substrate 10 are communicated with each otherthrough the ink supply paths 14 and the communicating paths 100. Here,with reference to FIG. 3, the communicating path 100 will be describedin detail. Note that FIG. 3 is a cross-sectional view showing a passagestructure of the ink-j et recording head according to embodiment 1. Asshown in FIG. 3, the communicating paths 100 are provided so as to beseparate from each other for each of the pressure generating chambers 12between the respective ink supply paths 14 and the communicating portion13. Together with the ink supply paths 14, the communicating paths 100form separate passages between the respective pressure generatingchambers 12 and the reservoir 110.

To be more specific, the partitions 11 at the both sides in the widthdirection of the pressure generating chamber 12 are provided so as toextend to the vicinity of an end of the reservoir portion 32 at thepressure generating chamber 12 side. Specifically, in this embodiment,the partitions 11 at the both sides in the width direction of thepressure generating chamber 12 are provided so as to extend to thevicinity of an end of a junction portion between the passage-formingsubstrate 10 and the reservoir forming plate 30 at the reservoir portion32 side. By extending the respective partitions 11 as described above,wall portions 11 a are formed between the respective ink supply paths 14and the communicating portion 13. Accordingly, a space between the inksupply paths 14 and the communicating portion 13 is divided by thesewall portions 11 a and the respective communicating paths 100 areformed.

Moreover, it is preferable that a width of the communicating path 100 isformed to be relatively wide. For example, it is preferable that arelationship between the width w₁ of the communicating path 100 and thewidth w₂ of the pressure generating chamber 12 satisfies w₁≧w₂.Furthermore, it is preferable that a relationship between the width w₁of the communicating path 100 and the width w₃ of the ink supply path 14satisfies w₁≧2×w₃. As described above, by providing the communicatingpath 100 to have a predetermined size, a desired ink supply property canbe obtained. Here, as ink, used is one having viscosity within a rangeof about 2.0 to 12.0 mPa·sec in an environment with a temperature withina range of about 10 to 40° C. To be more specific, as normal ink, onehaving viscosity within a range of about 2.0 to 6.5 mPa·sec isenumerated and, as high-viscosity pigmented ink, one having viscositywithin a range of about 8 to 11 mPa·sec is enumerated.

As described above, in this embodiment, the communicating paths 100 areprovided with the predetermined width so as to be separate from eachother for each of the pressure generating chambers 12 by use of the wallportions 11 a in a region facing the junction portion between thepassage-forming substrate 10 and the reservoir forming plate 30, theregion being positioned at the one end of the pressure generatingchambers 12 in the longitudinal direction. Specifically, thecommunicating paths 100 are provided between the respective ink supplypaths 14 and the reservoir 110. Thus, in ink ejection, ink flowing outtoward the reservoir 110 from the adjacent ink supply paths 14 do notinterfere with each other and occurrence of crosstalks can be prevented.Therefore, regardless of whether or not ink droplets are ejected fromthe adjacent nozzle orifices 21, a stable ink ejecting property can beobtained. Moreover, it is possible to shorten a length of the ink supplypath without generating crosstalk. Therefore, it is also made possibleto substantially enhance a damping property of meniscus and to realizehigh-speed drive of the head.

Moreover, in the present invention, it is preferable that, by providingthe wall portion ha to have a predetermined length or more, the lengthL₁ of the communicating path 100 (see FIG. 3) is set to a predeterminedlength or more. Specifically, it is preferable that the length of thecommunicating path 100 is set to the thickness of the passage-formingsubstrate 10 or more. Note that the length L₁ of the communicating path100 corresponds to a region where the width w₁ of the communicating path100 is secured. Accordingly, in the ink ejection, the ink flowing outtoward the reservoir 110 from the adjacent ink supply paths 14 flows outseparately to the reservoir 110 along the communicating paths 100 and donot interfere with each other. Thus, the occurrence of crosstalk can beeffectively prevented. For example, in this embodiment, the thickness ofthe passage-forming substrate 10 is set to about 70 _(″)m and the lengthof the communicating path 100 is set to about 100 _(″)m. Note that, bysetting the length of the communicating path 100 to the thickness of thepassage-forming substrate 10 or more as described above, althoughdescribed later in detail, it is possible to secure a sufficient lengthL of the junction portion of the reservoir forming plate 30 and thepassage-forming substrate 10 between the piezoelectric element holdingportion 31 and the reservoir portion 32.

Here, it is preferable that the length L of the junction portion (seeFIG. 2) of the passage-forming substrate 10 and the reservoir formingplate 30 between the piezoelectric element holding portion 31 and thereservoir 110 is 200 _(″)m or more. Accordingly, a distance between thepiezoelectric element holding portion 31 and the reservoir portion 32can be secured. Thus, it is possible to prevent moisture contained inthe ink in the reservoir 110 from entering the piezoelectric elementholding portion 31 and to surely prevent destruction of thepiezoelectric elements 300 due to the moisture. Moreover, since ajunction area between the passage-forming substrate 10 and the reservoirforming plate 30 is increased, there is also an effect that rigidity ofboth members can be sufficiently ensured and durability of the head canbe improved.

Note that it is preferable that the ends of the wall portions 11 a,which form the communicating paths 100, at the reservoir portion 32 sideare positioned in a region which faces the junction portion where thepassage-forming substrate 10 and the reservoir forming plate 30 arejoined. This is because, if the ends of the wall portions 11 a protrudein the communicating portion 13, the ends thereof will obstructformation of the reservoir 110 in a manufacturing process to bedescribed later by penetrating the elastic film 50 and the insulatingfilm 55, which separate the communicating portion 13 and the reservoirportion 32.

Moreover, in the present invention, it is preferable that a distancebetween the end of the partition 11 (the wall portion 11 a) at thereservoir portion 32 side and the reservoir portion 32 is set to beshort. Specifically, as shown in FIG. 4, it is preferable that thedistance S between the end of the partition 11 at the reservoir portion32 side and the reservoir portion 32 is set to be shorter than thethickness of the passage-forming substrate 10. Thus, the partition 11 isprovided so as to extend to the vicinity of the end of the reservoirportion 32 at the pressure generating chamber 12 side. Accordingly, aspace between the ink supply path 14 and the communicating portion 13(the reservoir 110), to be more specific, a space which is formed ofonly the passage-forming substrate 10 and which extends in the widthdirection of the pressure generating chamber 12 can be divided by thewall portion 11 a and be reduced. Consequently, interference between inkflowing out from adjacent communicating paths 100A can be reduced andthe occurrence of crosstalk can be prevented.

Moreover, in a region opposite to the reservoir portion 32 of thereservoir forming plate 30, the through-hole 33 which penetrates thereservoir forming plate 30 in its thickness direction is provided. Thelead electrode 90 extracted from each piezoelectric element 300 has itsend and the vicinity thereof exposed in the through-hole 33. As thereservoir forming plate 30 described above, a material havingapproximately the same coefficient of thermal expansion as that of thepassage-forming substrate 10, such as, for example, glass, a ceramicsmaterial or the like is preferably used. In this embodiment, thereservoir forming plate 30 is formed by use of a single crystal siliconsubstrate, which is the same material as that of the passage-formingsubstrate 10.

Note that, in a region corresponding to the reservoir portion 32 of thereservoir forming plate 30, a compliance plate 40 including a sealingfilm 41 and a fixed plate 42 is joined. Here, the sealing film 41 ismade of a material having low rigidity and flexibility (for example, apolyphenylene sulfide (PPS) film with a thickness of 6 μm) and thissealing film 41 seals one surface of the reservoir portion 32. Moreover,the fixed plate 42 is formed by use of a hard material such as metal(for example, stainless-steel (SUS) with a thickness of 30 μm or thelike). A region of this fixed plate 42, the region corresponding to thereservoir 110, is an opening portion 43 which is obtained by entirelyremoving the fixed plate 42 in the region in its thickness direction.Thus, the one surface of the reservoir 110 is sealed by use of only thesealing film 41 having flexibility.

The ink-jet recording head of this embodiment described above takes inink from unillustrated ink supply means and fills the inside thereoffrom the reservoir 110 to the nozzle orifices 21 with the ink.Thereafter, in accordance with a driving signal from an unillustrateddrive IC, the head applies drive voltages between the respective lowerelectrode film 60 and upper electrode film 80 which correspond to therespective pressure generating chambers 12. Accordingly, the elasticfilm 50, the insulating film 55 and the piezoelectric element 300 aredisplaced. Thus, the pressure in the respective pressure generatingchambers 12 are increased and ink droplets are ejected from the nozzleorifices 21.

TEST EXAMPLE

Here, a head having communicating paths provided therein (example) and ahead in which no communicating paths were provided and a space formed ofonly a passage-forming substrate was provided across an arrangementdirection of respective pressure generating chambers between ink supplypaths and a reservoir (comparative example) were prepared. Accordingly,a test for comparing crosstalk rates (%) of the both heads was carriedout. To be more specific, one nozzle to be a reference (referencenozzle) was determined, an ejecting speed when ink was ejected only fromthe reference nozzle was set as a reference value “0” and an ejectingspeed of ink droplets to be ejected from the reference nozzle when theink was ejected from the reference nozzle and nozzles at both sidesthereof at the same time was measured. Thereafter, while increasing thenumber of nozzles, from which the ink was simultaneously ejected, by 2,transition (rate of change) of the ejecting speed in the referencenozzle was examined. FIG. 5 shows a result thereof. Note that, in FIG.5, the rate of change of the ejecting speed in the reference nozzle isshown as the crosstalk rate (%).

As shown in FIG. 5, as to the head of the comparative example, when thenumber of simultaneous ejections reaches about 20, an increasing rate ofthe ejecting speed in the reference nozzle, that is, the crosstalk rateis increased to about 20% and is eventually increased close to 25%. Onthe other hand, as to the head of the example, when the number ofsimultaneous ejections reaches about 20, although the crosstalk rate isincreased to about 15% with the same transition as that of thecomparative example, the rate subsequently remains stable within a rangebelow 20%. As is clear from the result described above, it is found thatthe crosstalk rate in the head of the example is relatively about 10%lower than that in the head of the comparative example. Therefore, as inthe case of the head of the example, occurrence of crosstalk in inkejection can be reduced by providing the communicating paths.

Although the one example of the ink-jet recording head of the presentinvention has been described above, a manufacturing method thereof isnot particularly limited. Note that, with reference to FIGS. 6 and 7, anexample of a method of manufacturing the ink-jet recording headaccording to this embodiment will be described below. FIGS. 6 and 7 arecross-sectional views of the pressure generating chamber 12 in thelongitudinal direction.

First, as shown in FIG. 6( a), a wafer of a single crystal siliconsubstrate to be the passage-forming substrate 10 is thermally-oxidizedin a diffusion furnace heated to about 1100° C. Thus, the elastic film50 is formed all over the wafer. Thereafter, as shown in FIG. 6( b), theinsulating film 55 made of zirconium oxide or the like is formed on theelastic film 50. Next, as shown in FIG. 6( c), after the lower electrodefilm 60 made of platinum and iridium, for example, is formed on theentire surface of the insulating film 55, the lower electrode film 60 ispatterned to have a predetermined shape. Subsequently, as shown in FIG.6( d), the piezoelectric layer 70 made of, for example,lead-zirconate-titanate (PZT) and the upper electrode film 80 made of,for example, iridium are sequentially laminated and these layers aresimultaneously patterned to form the piezoelectric element 300.

Next, as shown in FIG. 7( a), the lead electrode 90 made of, forexample, gold (Au) or the like is formed all over the passage-formingsubstrate 10 and is patterned for each piezoelectric element 300. Thesteps described above are included in a film formation process. Next, asshown in FIG. 7( b), the insulating film 200 made of an inorganicinsulating material, in this embodiment, aluminum oxide (Al₂O₃) isformed and patterned to have a predetermined shape. Specifically, theinsulating film 200 is formed all over the passage-forming substrate 10and, thereafter, the insulating film 200 in regions which face theconnection portion 60 a of the lower electrode film 60 and theconnection portion 90 a of the lead electrode 90 is removed. Note that,in this embodiment, together with the insulating film 200 in the regionswhich face the connection portions 60 a and 90 a, the insulating film200 in a region other than the pattern region including the leadelectrode 90 and the respective layers constituting the piezoelectricelement 300 is also removed. Needless to say, only the insulating film200 in the regions which face the connection portions 60 a and 90 a maybe removed. In either case, the insulating film 200 may be formed so asto cover the pattern region including the lead electrode 90 and therespective layers constituting the piezoelectric element 300, except theconnection portion 60 a of the lower electrode film 60 and theconnection portion 90 a of the lead electrode 90. Moreover, although amethod for removing the insulating film 200 is not particularly limited,it is preferable to use dry etching such as ion milling, for example.Thus, selective removal of the insulating film 200 can be performedwell.

Next, as shown in FIG. 7( c), the reservoir forming plate 30, in whichthe piezoelectric element holding portion 31, the reservoir portion 32and the like are previously formed, is joined with the passage-formingsubstrate 10 at the piezoelectric element 300 side with an adhesiveinterposed therebetween. Note that the reservoir forming plate 30 asdescribed above also plays a role in protecting the respectivepiezoelectric elements 300 from an alkaline solution in formation of thepressure generating chambers 12 and the like by subjecting thepassage-forming substrate 10 to an anisotropic etching process in aprocess to be described later.

Thereafter, the single crystal silicon substrate (the passage-formingsubstrate 10) is subjected to an anisotropic etching process by use ofthe alkaline solution described above. Thus, the pressure generatingchamber 12, the communicating portion 13, the ink supply path 14 and thecommunicating path 100 are formed. To be more specific, as shown in FIG.7( d), after a mask pattern 51 is formed on a surface opposite to ajoint surface of the passage-forming substrate 10 and the reservoirforming plate 30, the passage-forming substrate 10 is subjected to ananisotropic etching process by use of the mask pattern 51. Thus, thepressure generating chamber 12, the communicating portion 13, the inksupply path 14 and the communicating path 100 are formed. Note that, inperforming the anisotropic etching as described above, the etching isperformed in a state where the surface of the reservoir forming plate 30is sealed by use of a protective film or the like. Moreover, at thistime, the reservoir 110 is formed by penetrating the elastic film 50 andthe insulating film 55, which are positioned at a boundary between thereservoir portion 32 and the communicating portion 13. As describedabove, in this embodiment, the ink supply path 14 and the like can beprovided by penetrating the passage-forming substrate 10 in itsthickness direction. Thus, by patterning the mask pattern 51 with highprecision, the ink supply path 14, the communicating path 100 and thelike can be formed with high precision. Therefore, a stable ink ejectingproperty is obtained.

Next, the nozzle plate 20 having the nozzle orifices 21 drilled thereinis joined with a surface of the passage-forming substrate 10, which isopposite the reservoir forming plate 30. Note that, thereafter, thecompliance plate 40 is joined on the reservoir forming plate 30, a driveIC is mounted on the reservoir forming plate 30 and the connectionportion 60 a of the lower electrode film 60 and the connection portion90 a of the lead electrode 90 are connected to the drive IC by use ofconnection wiring formed of bonding wires. Accordingly, thepiezoelectric element 300 and the drive IC are electrically connected toeach other. After the drive IC is mounted on the reservoir forming plate30 as described above, the respective members such as thepassage-forming substrate 10 and the reservoir forming plate 30 aredivided into pieces with a chip size. Thus, the ink-jet recording headof this embodiment as shown in FIG. 1 is manufactured.

Other Embodiments

Although the embodiment of the present invention has been describedabove, it is needless to say that the present invention is not limitedto the embodiment described above. For example, in the embodimentdescribed above, the ink supply path 14 is formed by narrowing thepassage in the width direction. However, without being limited thereto,the ink supply path may be formed by narrowing the passage in thethickness direction of the passage-forming substrate. Note that, in thiscase, the ink supply path is formed, for example, by subjecting thepassage-forming substrate to an anisotropic etching (half-etching)process in its thickness direction.

Moreover, in the embodiment described above, the piezoelectric elements300 are formed inside the piezoelectric element holding portion 31 ofthe reservoir forming plate 30. However, without being limited thereto,the piezoelectric element holding portion 31 does not have to beprovided. Also in this case, the surfaces of the piezoelectric elements300 and the lead electrode 90 are covered with the insulating film 200made of the inorganic insulating material. Thus, destruction of thepiezoelectric layer 70 due to moisture (humidity) is surely prevented.

Furthermore, in the embodiment described above, the piezoelectricelements 300 are covered with the insulating film 200. However, withoutbeing limited thereto, the piezoelectric elements do not have to becovered with the insulating film.

Furthermore, in the embodiment described above, the air release hole 31a which has one end communicating with the piezoelectric element holdingportion 31 and the other end released to the atmosphere is provided inthe reservoir forming plate 30 and the piezoelectric element holdingportion 31 is released to the atmosphere. However, without being limitedthereto, the piezoelectric element holding portion may be sealed withoutproviding the air release hole. In this case, destruction of thepiezoelectric elements due to moisture (humidity) from the air releasehole is surely prevented.

Moreover, in the embodiment described above, the thin-film ink-jetrecording head manufactured by applying the deposition and lithographyprocesses thereto was taken as an example. However, it is needless tosay that the present invention is not limited thereto. For example, thepresent invention can also be adopted in a thick-film ink-jet recordinghead manufactured by use of a method of attaching a green sheet and thelike.

Furthermore, the ink-jet recording head of the respective embodimentsdescribed above constitutes a part of a recording head unit, whichincludes ink passages communicating with ink cartridges and the like,and is mounted on an ink-jet recording apparatus. FIG. 8 is a schematicview showing an example of the ink-jet recording apparatus. As shown inFIG. 8, in recording head units 1A and 1B having the ink-jet recordingheads, cartridges 2A and 2B constituting ink supply means are providedso as to be detachable. A carriage 3 mounting the recording head units1A and 1B thereon is provided on a carriage shaft 5 attached to anapparatus body 4 so as to be movable in an axial direction. Theserecording head units 1A and 1B, for example, eject a black inkcomposition and a color ink composition, respectively.

Accordingly, driving force of a drive motor 6 is transmitted to thecarriage 3 through a plurality of gears (not shown) and a timing belt 7.Thus, the carriage 3 mounting the recording head units 1A and 1B thereonis moved along the carriage shaft 5. Meanwhile, a platen 8 is providedalong the carriage shaft 5 in the apparatus body 4 and a recording sheetS which is a recording medium such as paper, and which is fed by anunillustrated paper feeding roller or the like, is conveyed on theplaten 8.

Note that, in the embodiment described above, the ink-jet recording headwhich ejects ink as a liquid jet head and the ink-jet recordingapparatus have been described as an example. However, the presentinvention is aimed widely at general liquid jet heads and liquid jetapparatuses. As the liquid jet head, for example, enumerated are: arecording head used in an image recording apparatus such as a printer; acolor material jet head used for manufacturing color filters of a liquidcrystal display and the like; an electrode material jet head used forforming electrodes of an organic EL display, a field emission display(FED) and the like; a bioorganic matter jet head used for manufacturingbiochips; and the like.

1. A liquid jet head comprising: a passage-forming substrate in which aplurality of pressure generating chambers communicating with nozzleorifices are arranged; piezoelectric elements which are provided on thepassage-forming substrate with a vibration plate interposed therebetweenand each of which includes a lower electrode, a piezoelectric layer andan upper electrode; and a reservoir forming plate which is joined with asurface of the passage-forming substrate at the piezoelectric elementside and has a reservoir portion provided therein, the reservoir portionconstituting a part of a reservoir that is a common liquid chamber ofthe respective pressure generating chambers, wherein the reservoir isformed of the reservoir port ion and a communicating portion provided inthe passage-forming substrate, partitions at both sides in a widthdirection of the pressure generating chambers are provided to extend tothe vicinity of an end of the reservoir portion at the pressuregenerating chamber side and thus liquid supply paths, each of whichcommunicates with each of the pressure generating chambers and has awidth smaller than that of the pressure generating chamber, andcommunicating paths, each of which allows the liquid supply path and thecommunicating portion to communicate with each other and has a widthlarger than that of the liquid supply path, are provided while beingseparated for each of the pressure generating chambers by thepartitions, and wherein a distance between an end of each of thepartitions at the reservoir portion side and the reservoir portion isshorter than the thickness of the passage-forming substrate.
 2. Theliquid jet head according to claim 1, wherein a relationship between thewidth w₁ of the communicating path and the width w₂ of the pressuregenerating chamber satisfies w₁≧w₂.
 3. The liquid jet head according toclaim 2, wherein a relationship between the width w₁ of thecommunicating path and the width w₃ of the liquid supply path satisfiesw₁≧2×w₃.
 4. A liquid jet apparatus comprising: the liquid jet headaccording to claim
 3. 5. A liquid jet apparatus comprising: the liquidjet head according to claim
 2. 6. The liquid jet head according to claim1, wherein a relationship between the width w₁ of the communicating pathand the width w₃ of the liquid supply path satisfies w₁≧2×w₃.
 7. Aliquid jet apparatus comprising: the liquid jet head according to claim6.
 8. The liquid jet head according to claim 1, wherein a length of thecommunicating path is equal to or longer than a thickness of thepassage-forming substrate.
 9. A liquid jet apparatus comprising: theliquid jet head according to claim
 8. 10. The liquid jet head accordingto claim 1, wherein the piezoelectric elements are covered with aninsulating film made of an inorganic insulating material.
 11. The liquidjet head according to claim 10, wherein the insulating film is made ofAl₂O₃.
 12. A liquid jet apparatus comprising: the liquid jet headaccording to claim
 11. 13. A liquid jet apparatus comprising: the liquidjet head according to claim
 10. 14. The liquid jet head according toclaim 1, wherein, in the reservoir forming plate, a piezoelectricelement holding portion capable of securing a space without inhibitingmovement of the piezoelectric elements is provided in a region whichfaces the piezoelectric elements, and a region between the piezoelectricelement holding portion and the reservoir portion in the reservoirforming plate is a junction portion between the reservoir forming plateand the passage-forming substrate.
 15. The liquid jet head according toclaim 14, wherein ends of the partitions at the reservoir portion sideare positioned in a region which faces the junction portion.
 16. Aliquid jet apparatus comprising: the liquid jet head according to claim15.
 17. The liquid jet head according to claim 14, wherein a length ofthe junction portion is equal to or longer than 200 μm.
 18. A liquid jetapparatus comprising: the liquid jet head according to claim
 17. 19. Theliquid jet head according to claim 14, further comprising: an airrelease hole which has one end communicating with the piezoelectricelement holding portion and the other end released to the atmosphere.20. A liquid jet apparatus comprising: the liquid jet head according toclaim
 19. 21. A liquid jet apparatus comprising: the liquid jet headaccording to claim
 14. 22. The liquid jet head according to claim 1,wherein the thickness of the passage-forming substrate is equal to orshorter than 100 μm.
 23. A liquid jet apparatus comprising: the liquidjet head according to claim
 22. 24. The liquid jet head according toclaim 1, wherein the pressure generating chambers are formed bysubjecting a single crystal silicon substrate to an anisotropic etchingprocess.
 25. A liquid jet apparatus comprising: the liquid jet headaccording to claim
 24. 26. A liquid jet apparatus comprising: the liquidjet head according to claim
 1. 27. A liquid jet apparatus comprising:the liquid jet head according to claim 26.